Current color silver halide display materials utilize three color forming layers comprised of a red sensitive cyan dye forming layer, a green light sensitive magenta dye forming layer and a blue light sensitive yellow dye forming layer. In order to increase performance of color silver halide display materials in digital printers, there is a desire to have higher gamma at sub-microsecond exposure times in all three color records. Due to the large grain size of the blue light sensitive emulsion, the location of conventionally designed blue light sensitive yellow dye forming layers, and the high intensity reciprocity performance of conventionally sensitized blue light sensitive emulsions, the gamma of the blue light sensitive color record can be a limiting factor. These effects are especially evident in areas of high dye density, that is in the shoulder and Dmax (area of maximum density) regions. For instance, in the case of the blue light sensitive layer, a low shoulder would lead to black areas going blue and yellow colors desaturating.
One common way to increase gamma is increase the silver coverage of the emulsion. However, increased silver causes a number of problems. In particular, higher silver coverage leads to reduction in develop ability. This results in a lowering of neutral gamma for a given silver coverage and for a given time of development, or increased process sensitivity.
A further effect of using high coverage of emulsion is a deleterious loss of color purity. Typically, color photographic elements contain Dox scavenging interlayers (otherwise known as anticolor-mixing layers) to prevent interlayer color contamination. In the case of large grained emulsions, the scavenging layer may be increased in thickness or in concentration of the scavenging component in order to prevent formation of unwanted dye in adjacent layers. This also results in materials being wasted, since no dye is formed as a result of this process. In some instances, the very large grained emulsions produce a local concentration of Dox (oxidized developer) that is too high to be completely used by the appropriate coupler and/or scavenged by an anticolor mixing agent. For instance, in the case of large grained emulsions used in the blue layer, this can result in the formation of magenta colored spots in the photographic print from reaction of Dox formed in the blue layer with magenta coupler situated in the green layer.
When exposing conventional photographic materials by digital imaging there is a tendency for the images to have a defect commonly referred to as fringing which is a loss of image sharpness. This defect is most apparent at the edges of white areas of the prints bordering areas of higher density. Therefore there is a need to minimize fringing by silver halide materials exposed by digital means.
U.S. Pat. Nos. 5,066,575, 5,250,400, and 5,023,170 describe the pyrazoloazole type coupler class.
U.S. Pat. No. 4,404,274 describes the ketomethylene coupler class.